In the state of the art, a variety of systems and techniques are known to intervene on specific problems of the spine, such as abnormal curvature of the spine, injuries to the same, etc. The intervention on these types of spine-specific problems frequently requires the stabilization of a portion of the spine portion so as to facilitate the fusion of two or more vertebrae together in a single bone agglomeration.
This type of intervention is frequently employed for the correction of many pathological conditions of the spine such as, for example, degenerative diseases of the bone disc elements, scoliosis, spinal stenosis, or the like. Not infrequently, these corrective measures require the use of implants, such as, for example, bone grafts. The stabilization of the spine allows the creation of a bone tissue in the intervertebral part; in this way, a part of the spine is fused into a single bone body.
The stabilization of the spine is a known technique, and a variety of methods and devices have been developed for the correction of many pathologies that affect characteristically this body part in order to stabilize its configuration, facilitating the vertebral fusion at various levels. One of these known systems provides that a bar is arranged longitudinally along the portion of the spine which needs the intervention. This bar is shaped in such a way as to represent the correct anatomical shape which is characteristic of that specific portion of a healthy spine.
With this method, therefore, the bar is positioned along the spine to engage various vertebrae, as needed. It should be noted that, typically, in this type of surgery, two parallel bars are used that are arranged at the sides of the central area of the spine. Therefore, during the surgery, the pair of bars is fixed to the spine by means of various fixing means, including, for example, screws. These screws are attached to the bone structure, typically to the vertebral pedicle.
The inclination of the bar and, consequently, the positioning of the fixing screws varies depending on the type of correction to be done and, of course, from vertebra to vertebra. It seems clear that for a successful surgery, the procedure needs to properly fix both the corrective bar and the screws. In order to obtain a correct positioning of the elements, according to the needs of the patient, polyaxial screws are utilized.
The implant of the polyaxial screws, bars and any necessary fixing means, may require typically somewhat invasive interventions resulting in injuries to the skin and muscle tissues of the patient. This surgery may require rather long hospitalization and rehabilitation times.
In order to reduce the invasiveness of the surgery, the operative technique was directed toward minimally invasive techniques able to significantly reduce the trauma to the tissues, with benefits for the patient including, for example, shorter hospitalization times, lower postoperative pain, less rehabilitation, and with benefits for the hospitals, including shorter hospitalization times, fewer costs, and fewer resources for the rehabilitation. To address the needs of this type of minimally invasive interventions, instruments capable of allowing the surgeon to secure the polyaxial screws in the desired position have been developed, also through an incision of limited size on the patient's body, along with the possibility of implanting the bars in the desired position through the instruments.
An example of this type of surgery instruments is illustrated in the U.S. Patent Application Publication No. 2013/0144349 to Lanx Inc., Broomfield, Colo. (USA). This approach discloses an instrument to facilitate minimally invasive surgery procedures. The instrument comprises an outer sleeve, in turn comprising a first and a second elongated sleeve, each having a distal end and a proximal end. The inner sleeve has a first and a second channel extending between the first and the second elongated sleeve, starting from the distal end. The first and the second channel each have a length greater than the half of the total length of the first and second elongated sleeve. The outer sleeve includes a third and fourth elongated sleeve, each having a proximal and a distal end, the outer sleeve also comprises a third and a fourth channel extending between the third and the fourth elongated sleeve, starting from the distal end. The third and fourth channel each have a length greater than the half of the length of the third and fourth elongated sleeve. In that instrument, the inner sleeve is dimensioned in such a way as to be housed inside the outer sleeve. The instrument comprises a connecting element adapted to couple the two proximal ends of the first and second elongated sleeve with the proximal ends of the third and fourth elongated sleeve. It is also provided an alignment element to align the first channel with the third channel and the second channel with the fourth channel, when the inner sleeve is housed inside the outer sleeve. Additionally, the device has coupling means with an implant, these being adapted to secure the first and the second sleeve to the implant in a demountable manner.